If you choose to take retirement early you will not be eligible for a State Pension until you reach state pension age. You can find out what your state pension age will be from http://www.thepensionservice.gov.uk/.
You can also get a State Pension Forecast to see how much State Pension you will receive upon entitlement by visiting the Inland Revenue website, or writing to the forecasting team.
The Pension Forecasting Team
The Pension Service
Room TB001
Tyneview Park
Whitly Road
Newcastle upon Tyne
NE98 1BA
Telephone: 0845 3000 168 ( 8am to 8pm Monday to Friday)
TextPhone: 0845 3000 169
Website: http://www.thepensionservice.gov.uk/pensionforecast/
You may be asked questions to ensure your identity as well as provide background information and identification documents.